1. Field of the Invention
The present invention generally relates to a semiconductor optical switch. More specifically, the present invention relates to a semiconductor optical switch that switches transmission path for optical signal based on variation of reflectivity.
Priority is claimed on Japanese Patent Application No. 2007-200738, filed Aug. 1, 2007, the content of which is incorporated herein by reference.
2. Description of the Related Art
All patents, patent applications, patent publications, scientific articles, and the like, which will hereinafter be cited or identified in the present application, will hereby be incorporated by reference in their entirety in order to describe more fully the state of the art to which the present invention pertains.
There have been known various types of semiconductor optical switches. A typical example of the semiconductor optical switch includes an optical waveguide having a branching point at which an electrode is provided. Carrier injection may be made into the branching point of the waveguide, thereby changing or decreasing the refractive index of the branching point so that the branching point reflects an optical signal that has propagated through the incoming path of the waveguide, and then the reflected optical signal propagates through an outgoing reflection path. No carrier injection may be made into the branching point of the waveguide, thereby returning the refractive index to the original value so that the branching point allows the optical signal path. This typical type of the semiconductor optical switch is disclosed in Japanese Unexamined Patent Applications, First Publications, Nos. 05-165067, 2005-070199, 06-130236, 06-289339, and by Baujnn Li, Guozheng Li, Enke Liu, Zuimin Jiang, Chengwen Pei and Xun Wang, in Appl. Phys. Lett., pp. 1-3, 75 (1999).
The semiconductor optical switch can perform as an optical switch. The semiconductor optical switch has an insufficient extinction ratio that is defined as a ratio of output optical power in the ON-state to the OFF-state, as compared to the conventional switch. Such insufficiency of the extinction ratio can limit applicable fields to which the semiconductor optical switch is applicable. In general, the extinction ratio needs to be ranged about 20 dB to about 30 dB for practicing the optical switch. The typical type of the semiconductor optical switch controlling the refractive index often has a lower extinction ratio of about 10 dB.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved semiconductor optical switch. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.